The present invention relates to a novel cationic electrodeposition paint composition and a process for preparing the same, and more particularly to a cationic electrodeposition coating composition in which the electrodeposited coating film of the electrodeposition paint composition has an epoxy-acrylic double-layered structure, and in which an organic solvent content can be minimized, and a process for preparing the same. Further, the present invention relates to a pigment grinding vehicle suitable for electrodeposition coating of the cationic electrodeposition paint composition.
The cationic electrodeposition paint is widely used for primer coating of cars, household electric appliances, and industrial machines. Recent research at home and abroad on a cationic electrodeposition paint have concentrated on paints related to energy saving, safety and environmental considerations. Also, research on binders of electrodeposition coating have concentrated on developing high functional and high efficient electrodeposition paint having various purposes and characteristics. Among the research, studies on reducing an organic solvent emissions from paint operations are being developed. The motive for these studies is the regulation of emission of organic solvents for the protection of the environment. As examples of regulations related to the regulation of emission of organic solvents, a regulation for volatile organic compounds (VOC) of the Environment Office in U.S. and an atmospheric purification law in Germany can be illustrated. The former establishes a guideline for the amount of organic solvents in a paint, while the latter restricts the amount of organic solvents discharged from the paint used for coating a car. Since 20% of the amount of carbon dioxide discharged in the whole world are due to the coating industry (for example, organic solvent and combustion by means of a drying oven), the coating industry is a major cause of environmental pollution. Hence, the coating industry has become the subject of supervision. Presently, as an electrodeposition coating for primer coating, epoxy cationic electrodeposition paints are mainly used. However, these epoxy cationic electrodeposition paints are rich in organic solvents and these solvents are evaporated from the electrodeposition tank, thereby emitting an offensive odor in a workpiece. Also, these solvents are emitted during baking, so environmental pollution problems occur. Though these epoxy cationic electrodeposition paints have excellent properties such as chemical resistance, corrosion-resistance, adhesion etc., they are lacking in properties such as weather-resistance, yellowing resistance, etc.